Method of manufacturing vertical-cavity surface emitting laser and vertical-cavity surface emitting laser array

Abstract

A method of manufacturing a surface emitting laser element of a vertical cavity type comprises sequential accumulation that accumulates a reflecting mirror of a multilayered film layer at a lower side of the substrate, and accumulates semiconductor layers onto the reflecting minor at the lower side that comprises an active layer and a contact layer. The process includes forming a first layer of dielectric substance on the contact layer, forming an electrode of an annular shape on the contact layer that has an open part to be arranged for the first layer at an inner side of the open part, and forming a second layer of dielectric substance to cover the first layer and a gap formed between the first layer and the electrode of the annular shape. The accumulated semiconductor layers are etched to form a mesa post, using the electrode of the annular shape as a mask.

1. A method of manufacturing a surface emitting laser element of a vertical cavity type, comprising the steps of:
 sequentially accumulating a multilayered reflecting mirror and a plurality of semiconductor layers on a substrate, the plurality of semiconductor layers comprising an active layer, an ohmic contact layer that has a first dopant density and a conductivity type, and a spacer layer formed between the active layer and the ohmic contact layer that has a second dopant density that is less than the first dopant density and the conductivity type, the accumulating further comprising forming an electrical current narrowing layer that comprises an electrical current narrowing part and an electrical current injection part that is located substantially at a center of the electrical current narrowing part; 
 forming a first dielectric layer on the ohmic contact layer, wherein a diameter of the electrical current injection part is smaller than a diameter of the first dielectric layer; 
 forming an electrode on the ohmic contact layer, an open part of the electrode being substantially at a center of the ohmic contact layer, and the first dielectric layer being arranged at an inner side of the open part of the electrode; 
 forming a second dielectric layer covering the first dielectric layer and covering a gap which is formed between the first dielectric layer and the electrode, the second dielectric layer being a layer that is present in the manufactured surface emitting laser element; 
 etching the plurality of semiconductor layers and forming a mesa post that is accumulated on the semiconductor, wherein the electrode is a mask of the mesa post, wherein the forming the second dielectric layer occurs prior to the etching of the plurality of semiconductor layers; 
 forming a second multilayered reflecting mirror above the second dielectric layer by accumulating a multilayered film that is formed of a dielectric substance, after forming the mesa post, 
 wherein the first dielectric layer comprises a multilayered structure of a fourth dielectric layer on a lower side and a fifth dielectric layer on an upper side, and the fourth dielectric layer has optical thickness of approximately λ/4, where λ is a preferred emission wavelength of a laser. 
 
     
     
       2. The method of manufacturing the surface emitting laser element of the vertical cavity type according to  claim 1 ,
 wherein the accumulating further comprises accumulating a layer to be oxidized that is formed of an AlAs or an Al 1-x Ga x As (0<x<1) between the ohmic contact layer and the active layer, and 
 wherein the forming the electrical current narrowing layer that comprises the electrical current injection part further comprising forming the electrical current injection part of AlAs or Al 1-x Ga x As and forming the electrical current narrowing part of Al 2 O 3  or (Al 1-x Ga x ) 2 O 3 , by performing a selective oxidizing heat treatment that is performed after the formation of the mesa post. 
 
     
     
       3. The method of manufacturing the surface emitting laser element of the vertical cavity type according to  claim 2 ,
 wherein the accumulating further comprises accumulating a layer for an electrical current path in between the ohmic contact layer and the layer to be oxidized, that has a concentration of an acceptor which is approximately equivalent to the concentration of the acceptor in the ohmic contact layer. 
 
     
     
       4. The method of manufacturing the surface emitting laser element of the vertical cavity type according to  claim 1 ,
 wherein at least a part of the first dielectric layer that contacts the ohmic contact layer is formed of silicon nitride that has a higher composition ratio of nitrogen than the rest of the first dielectric layer. 
 
     
     
       5. A surface emitting laser element of the vertical cavity type, comprising:
 a substrate; 
 a multilayered reflecting minor that is accumulated on the substrate; 
 a plurality of semiconductor layers accumulated on the multilayered reflecting mirror, the plurality of semiconductor layers comprising:
 a structure of a mesa post, 
 an active layer, 
 an ohmic contact layer on a top of the plurality of semiconductor layers, wherein the ohmic contact layer has a conductivity type and a first dopant density, wherein the ohmic contact layer has an outer circumference corresponding to an outer circumference of the structure of the mesa post, and 
 a spacer layer formed between the active layer and the ohmic contact later, wherein the spacer layer has the conductivity type and a second dopant density, wherein the second dopant density is lower than the first dopant density, wherein the ohmic contact layer is formed on the spacer layer; 
 
 an electrode that is formed on the ohmic contact layer, an open part of the electrode being substantially at a center of the ohmic contact layer; 
 a first dielectric layer on the ohmic contact layer at an inner side of the open part of the electrode; 
 a second dielectric layer that covers the first dielectric layer covering a gap that is formed between the first dielectric layer and the electrode, wherein the second dielectric layer is formed before the structure of the mesa post is formed and is present in the manufactured surface emitting laser element; 
 an electrical current narrowing layer comprising an electrical current narrowing part and an electrical current injection part that is located substantially at a center of the electrical current narrowing part, wherein a diameter of the electrical current narrowing part is smaller than a diameter of the first dielectric layer; 
 a multilayered film that is formed on the second dielectric layer, wherein the multilayered film is formed of a dielectric substance, 
 wherein the first dielectric layer comprises a multilayered structure of a fourth dielectric layer at a lower side and a fifth dielectric layer at an upper side, and the fourth dielectric layer at the lower side has an optical thickness of approximately λ/4 when a preferred emission wavelength of a laser is (λ), and the multilayered film and the fifth dielectric layer configure a second multilayered reflecting mirror, in which the fifth dielectric layer at the upper side is also a bottom layer. 
 
     
     
       6. The surface emitting laser element of the vertical cavity type according to  claim 5 ,
 wherein the electrical current injection part is formed of an AlAs or an Al 1-x Ga x As (0<x<1) and the electrical current narrowing part is formed of an Al 2 O 3  or an (Al 1-x Ga x ) 2 O 3 , that are formed by a selective oxidizing heat treatment between the active layer and the ohmic contact layer. 
 
     
     
       7. The surface emitting laser element of the vertical cavity type according to  claim 6 ,
 wherein the layers of the semiconductor provide a layer for an electrical current path between the electrical current narrowing layer and the ohmic contact layer, that has a concentration of an acceptor that is approximately equivalent to a concentration of the acceptor in the ohmic contact layer. 
 
     
     
       8. The surface emitting laser element of the vertical cavity type according to  claim 5 ,
 wherein at least a part of the first dielectric layer that contacts the ohmic contact layer is formed of a silicon nitride which has a higher composition ratio of nitrogen than the rest of the first dielectric layer. 
 
     
     
       9. The surface emitting laser element of the vertical cavity type according to  claim 5 ,
 wherein the ohmic contact layer is not thicker than 50 nm, the concentration of an acceptor is not lower than 10 19  cm −3 , and a concentration of hydrogen is not higher than 10 18  cm −3 .